Airdrie
Clear Sky Chart
History

This sumarizes the distribution of each different forecast outcome for the Airdrie clear sky chart from 2005-11-06 to 2026-09-14.

This page is a summary of past forecasts. Even though it's based only on forecasts, some people use these pages as clue to a site's climate. But climate data based on actual observation should be preferred (if you can find it!).

Cloud, Transparency and Seeing forecasts are summarized individually. But because good observing conditions require a combination of minimum cloud cover, transparency and seeing, the individual forecast summaries can be difficult to interpret. The observing conditions section counts the combinations of conditions needed for common types of astronomical observation.

Observing Conditions

The following tables count the occurrence of the combinations of forecast and darkness conditions needed for different observations. Conditions are rated by by what percentage of the hours the observation would likely be attempted are usable.

Observation Type	Minimum conditions for hour to be usable				Out of hours
	Clear of Clouds	Transparency	Seeing	Sky Brightness
Planetary:	50%	(no limit)	Average	(no limit)	Nighttime Hours
Deep Sky:	70%	Average	(no limit)	5.9	Nighttime Hours
CCD Imaging:	70%	Below Average	Poor	(no limit)	Nighttime Hours

Percentages are of nighttime hours per month, or per year, when a particular observing conditions was met. Deep Sky percentages never exceed 50% because the moon is up half the time. Deep sky percentages are much lower for charts at high latitudes because of fewer dark hours in the summer.

Overall

By Month

Individual Forecasts

The length of each colored bar in the "occurrence of each Forecast" column is proportional to the number of times the chart forecast that color. The percentages are of the total number of hours per month, or per year, with a particular forecast. The colors as the same as those used in clear sky charts.

Note: Transparency probabilities are only counted for those hours that have 30% or less cloud cover. Seeing probabilities are only counted for those hours that have 80% or less cloud cover. If that's too tricky, try Observing Conditions instead.

Overall

		Occurrence of each Forecast	Data Points
Cloud Cover	Day	8% 8% 3 8% 5% 5% 5% 4 6% 8% 38%	154149
	Night	6% 9% 3 9% 5% 5% 5% 4 6% 8% 38%	145690
Transparency	Day	41% 5% 16% 25% 11% 2	153851
	Night	42% 5% 16% 24% 12% 2	145571
Seeing	Day	13% 10% 30% 29% 14% 4	17827
	Night	11% 8% 33% 33% 13% 2	26753

By Month

Percentage Cloud Cover NW (2006-)
Color Meanings: Overcast 90% covered 80% covered 70% covered 60% covered 50% covered 40% covered 30% covered 20% covered 10% covered Clear
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	2 7% 5% 13% 7% 8% 7% 4 7% 8% 31%	4125
	11th to 20th	Day	2 7% 3 9% 6% 6% 6% 5% 7% 8% 42%	4194
	21st to end	Day	3 6% 3 10% 6% 5% 5% 5% 6% 10% 44%	5186
February	1st to 10th	Day	3 12% 5% 12% 7% 5% 7% 4 7% 8% 28%	1680
	11th to 20th	Day	5% 9% 4 11% 8% 6% 7% 5% 8% 8% 29%	1826
	21st to end	Day	4 11% 5% 11% 6% 6% 6% 5% 7% 9% 31%	1683
March	1st to 10th	Day	2 9% 4 11% 6% 5% 6% 4 6% 10% 36%	4618
	11th to 20th	Day	4 11% 5% 10% 5% 4 5% 4 6% 8% 38%	5053
	21st to end	Day	8% 22% 7% 14% 6% 5% 4 4 5% 6% 19%	5694
April	1st to 10th	Day	7% 17% 5% 11% 5% 5% 5% 4 6% 8% 27%	2578
	11th to 20th	Day	10% 15% 5% 9% 7% 5% 4 4 6% 7% 28%	2700
	21st to end	Day	11% 13% 4 9% 5% 5% 4 4 5% 8% 30%	2730
May	1st to 10th	Day	11% 10% 3 7% 5% 4 5% 4 6% 7% 37%	8080
	11th to 20th	Day	11% 12% 4 9% 6% 6% 7% 6% 7% 8% 24%	8755
	21st to end	Day	12% 7% 3 8% 6% 6% 6% 4 6% 8% 34%	9649
June	1st to 10th	Day	17% 7% 2 9% 6% 5% 6% 5% 7% 8% 28%	3150
	11th to 20th	Day	18% 9% 3 9% 5% 5% 7% 5% 7% 7% 25%	3150
	21st to end	Day	9% 5% 2 7% 6% 6% 7% 5% 7% 9% 38%	3150
July	1st to 10th	Day	6% 5% 2 6% 4 4 5% 5% 7% 9% 47%	8820
	11th to 20th	Day	9% 4 2 5% 3 4 5% 5% 8% 10% 47%	8820
	21st to end	Day	7% 4 2 5% 3 4 4 3 5% 8% 54%	9374
August	1st to 10th	Day	7% 5% 2 6% 4 4 5% 4 7% 9% 47%	6441
	11th to 20th	Day	10% 6% 2 6% 5% 4 5% 5% 7% 10% 41%	6011
	21st to end	Day	7% 4 2 5% 3 4 4 3 6% 8% 55%	6570
September	1st to 10th	Day	11% 6% 3 6% 4 4 4 3 5% 8% 47%	2607
	11th to 20th	Day	14% 8% 2 5% 4 3 4 3 6% 7% 43%	2234
	21st to end	Day	9% 8% 2 7% 5% 4 4 4 6% 8% 44%	2200
October	1st to 10th	Day	7% 6% 3 7% 4 5% 5% 4 7% 10% 42%	3450
	11th to 20th	Day	5% 7% 2 7% 4 5% 6% 5% 8% 10% 42%	3000
	21st to end	Day	7% 7% 3 7% 6% 5% 5% 5% 5% 7% 44%	3200
November	1st to 10th	Day	7% 16% 5% 9% 5% 5% 5% 4 5% 8% 31%	1715
	11th to 20th	Day	5% 12% 3 8% 6% 5% 5% 4 6% 7% 38%	1589
	21st to end	Day	4 14% 4 10% 5% 5% 4 4 7% 10% 33%	1470
December	1st to 10th	Day	3 11% 5% 13% 7% 7% 5% 5% 6% 7% 31%	2360
	11th to 20th	Day	3 10% 4 10% 7% 8% 8% 5% 7% 7% 30%	2712
	21st to end	Day	2 9% 4 9% 5% 5% 5% 4 6% 7% 42%	3575
January	1st to 10th	Night	3 11% 5% 13% 8% 7% 7% 4 7% 7% 27%	8768
	11th to 20th	Night	2 7% 4 12% 6% 5% 6% 6% 7% 8% 39%	8761
	21st to end	Night	2 8% 4 10% 6% 6% 6% 4 6% 8% 39%	8994
February	1st to 10th	Night	4 10% 4 11% 8% 7% 6% 5% 6% 8% 31%	2940
	11th to 20th	Night	5% 11% 5% 11% 7% 6% 6% 5% 8% 8% 30%	2679
	21st to end	Night	2 11% 5% 11% 8% 5% 6% 5% 6% 8% 33%	2123
March	1st to 10th	Night	3 8% 4 13% 7% 6% 6% 5% 6% 10% 34%	5496
	11th to 20th	Night	5% 8% 4 10% 5% 6% 6% 5% 7% 8% 37%	5166
	21st to end	Night	8% 19% 6% 15% 7% 5% 4 4 6% 7% 21%	5521
April	1st to 10th	Night	8% 14% 3 11% 5% 5% 5% 5% 7% 8% 29%	2041
	11th to 20th	Night	10% 12% 6% 11% 6% 5% 4 5% 5% 7% 30%	1871
	21st to end	Night	11% 12% 5% 9% 6% 5% 5% 5% 6% 8% 30%	1890
May	1st to 10th	Night	11% 12% 4 8% 4 4 4 3 5% 7% 38%	4838
	11th to 20th	Night	12% 9% 3 8% 5% 5% 5% 5% 8% 10% 30%	4105
	21st to end	Night	9% 7% 3 8% 5% 6% 7% 5% 7% 8% 34%	4522
June	1st to 10th	Night	16% 9% 3 8% 5% 4 5% 5% 7% 6% 33%	1470
	11th to 20th	Night	17% 7% 4 6% 6% 5% 6% 5% 7% 7% 29%	1470
	21st to end	Night	9% 5% 2 6% 5% 6% 6% 4 8% 9% 40%	1470
July	1st to 10th	Night	5% 4 2 5% 4 4 5% 4 7% 9% 49%	4140
	11th to 20th	Night	7% 4 2 5% 3 4 5% 4 7% 8% 50%	4140
	21st to end	Night	8% 4 2 5% 3 4 3 3 4 9% 56%	4690
August	1st to 10th	Night	9% 6% 2 7% 4 4 4 3 6% 8% 46%	3709
	11th to 20th	Night	10% 6% 2 7% 4 4 5% 4 8% 11% 39%	4051
	21st to end	Night	6% 4 1 6% 4 4 4 4 7% 10% 50%	4578
September	1st to 10th	Night	11% 6% 2 5% 4 4 4 3 6% 8% 48%	2008
	11th to 20th	Night	13% 6% 2 5% 3 4 3 3 5% 8% 46%	2233
	21st to end	Night	9% 7% 2 5% 4 4 4 4 7% 8% 45%	2200
October	1st to 10th	Night	7% 7% 2 6% 4 4 4 4 6% 8% 48%	3745
	11th to 20th	Night	6% 8% 2 5% 4 5% 5% 4 6% 8% 47%	4147
	21st to end	Night	5% 7% 3 7% 5% 5% 5% 5% 7% 7% 43%	4600
November	1st to 10th	Night	7% 13% 5% 8% 5% 4 5% 4 6% 8% 35%	2782
	11th to 20th	Night	3 11% 4 8% 6% 6% 6% 4 6% 9% 37%	3029
	21st to end	Night	5% 11% 4 8% 6% 6% 5% 4 7% 9% 36%	3150
December	1st to 10th	Night	4 11% 4 11% 7% 7% 6% 5% 7% 9% 31%	5040
	11th to 20th	Night	4 11% 5% 13% 8% 7% 5% 4 6% 8% 29%	5700
	21st to end	Night	3 10% 4 9% 5% 5% 5% 5% 6% 7% 40%	7623

Transparency (when cloud cover <= 30%)
Color Meanings: Too cloudy to forecast Poor Below Average Average Above average Transparent
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	49% 4 11% 21% 13% 2	4125
	11th to 20th	Day	39% 5% 15% 19% 18% 4	4215
	21st to end	Day	36% 5% 15% 30% 13% 1	5187
February	1st to 10th	Day	51% 5% 14% 17% 11% 2	1680
	11th to 20th	Day	49% 5% 12% 22% 10% 1	1835
	21st to end	Day	47% 5% 12% 22% 12% 2	1683
March	1st to 10th	Day	41% 6% 15% 22% 16% 1	4618
	11th to 20th	Day	41% 5% 14% 24% 15% 1	5054
	21st to end	Day	64% 6% 12% 12% 6% 1	5694
April	1st to 10th	Day	54% 6% 14% 18% 8% 1	2578
	11th to 20th	Day	53% 6% 11% 20% 9% 1	2700
	21st to end	Day	51% 4 13% 21% 9% 1	2730
May	1st to 10th	Day	44% 4 11% 26% 12% 2	8080
	11th to 20th	Day	51% 7% 12% 21% 7% 1	8759
	21st to end	Day	46% 5% 16% 25% 7%	9650
June	1st to 10th	Day	51% 6% 14% 19% 9% 1	3150
	11th to 20th	Day	54% 6% 14% 17% 7% 1	3150
	21st to end	Day	39% 7% 20% 25% 8% 1	3150
July	1st to 10th	Day	30% 7% 19% 29% 14% 2	8746
	11th to 20th	Day	31% 6% 19% 28% 12% 4	8739
	21st to end	Day	28% 5% 16% 28% 19% 5%	9170
August	1st to 10th	Day	32% 5% 18% 33% 9% 3	6424
	11th to 20th	Day	37% 6% 25% 25% 6% 1	6051
	21st to end	Day	27% 4 18% 38% 12% 1	6569
September	1st to 10th	Day	36% 4 17% 26% 13% 5%	2607
	11th to 20th	Day	39% 4 15% 27% 13% 1	2234
	21st to end	Day	38% 5% 14% 28% 12% 3	2200
October	1st to 10th	Day	36% 5% 19% 33% 6% 1	3450
	11th to 20th	Day	36% 5% 20% 24% 13% 2	3000
	21st to end	Day	38% 5% 11% 33% 12% 1	3200
November	1st to 10th	Day	50% 7% 10% 20% 11% 2	1715
	11th to 20th	Day	44% 4 16% 24% 10% 2	1589
	21st to end	Day	45% 4 16% 22% 10% 2	1470
December	1st to 10th	Day	51% 5% 13% 22% 7% 2	2360
	11th to 20th	Day	50% 4 19% 19% 7% 1	2714
	21st to end	Day	39% 5% 11% 23% 18% 4	3575
January	1st to 10th	Night	53% 5% 12% 19% 10% 2	8769
	11th to 20th	Night	41% 5% 17% 20% 13% 5%	8802
	21st to end	Night	42% 4 17% 25% 12% 1	8994
February	1st to 10th	Night	50% 5% 11% 19% 13% 3	2940
	11th to 20th	Night	49% 5% 12% 20% 12% 2	2680
	21st to end	Night	46% 5% 11% 23% 13% 2	2123
March	1st to 10th	Night	43% 6% 17% 20% 12% 2	5496
	11th to 20th	Night	41% 7% 14% 23% 14% 1	5166
	21st to end	Night	61% 5% 11% 14% 8% 1	5521
April	1st to 10th	Night	50% 6% 13% 20% 11% 1	2041
	11th to 20th	Night	52% 4 11% 21% 10% 1	1871
	21st to end	Night	49% 5% 13% 22% 9% 2	1890
May	1st to 10th	Night	46% 4 11% 23% 14% 2	4835
	11th to 20th	Night	45% 5% 15% 25% 9%	4105
	21st to end	Night	44% 6% 18% 26% 6%	4526
June	1st to 10th	Night	49% 5% 16% 19% 11% 1	1470
	11th to 20th	Night	50% 6% 15% 19% 7% 3	1470
	21st to end	Night	37% 6% 23% 26% 7% 1	1470
July	1st to 10th	Night	29% 6% 20% 30% 13% 2	4105
	11th to 20th	Night	30% 5% 21% 28% 12% 4	4098
	21st to end	Night	27% 5% 19% 29% 17% 4	4589
August	1st to 10th	Night	35% 5% 15% 30% 13% 2	3701
	11th to 20th	Night	38% 6% 27% 23% 5%	4077
	21st to end	Night	27% 5% 21% 35% 10% 1	4578
September	1st to 10th	Night	35% 4 16% 27% 14% 4	2008
	11th to 20th	Night	36% 4 16% 27% 13% 4	2233
	21st to end	Night	34% 5% 18% 26% 14% 3	2200
October	1st to 10th	Night	33% 5% 18% 26% 17% 1	3745
	11th to 20th	Night	35% 4 18% 26% 15% 2	4147
	21st to end	Night	37% 5% 11% 32% 13% 1	4600
November	1st to 10th	Night	47% 5% 13% 22% 11% 2	2782
	11th to 20th	Night	43% 5% 16% 22% 13% 1	3029
	21st to end	Night	43% 5% 16% 22% 10% 3	3150
December	1st to 10th	Night	49% 6% 16% 21% 7% 2	5040
	11th to 20th	Night	52% 4 17% 18% 8% 1	5697
	21st to end	Night	40% 4 10% 24% 16% 4	7623

Seeing (when cloud cover <= 80%)
Color Meanings: Too cloudy to forecast Bad 1/5 Poor 2/5 Average 3/5 Good 4/5 Excellent 5/5
Month	Days in Month		Occurrence of each Forecast	Data Points
January	1st to 10th	Day	6% 11% 37% 27% 12% 7%	220
	11th to 20th	Day	10% 12% 41% 24% 11% 2	220
	21st to end	Day	9% 10% 38% 30% 11% 2	242
February	1st to 10th	Day	11% 15% 35% 21% 11% 5%	220
	11th to 20th	Day	7% 11% 39% 32% 9% 2	321
	21st to end	Day	9% 13% 34% 30% 13% 2	399
March	1st to 10th	Day	9% 16% 35% 28% 10% 3	540
	11th to 20th	Day	10% 14% 36% 27% 10% 2	540
	21st to end	Day	16% 16% 35% 21% 9% 4	594
April	1st to 10th	Day	16% 16% 33% 24% 9% 2	540
	11th to 20th	Day	15% 14% 31% 28% 10% 2	532
	21st to end	Day	20% 14% 25% 27% 12% 2	540
May	1st to 10th	Day	20% 11% 27% 26% 14% 3	595
	11th to 20th	Day	18% 8% 25% 29% 16% 4	775
	21st to end	Day	18% 9% 21% 30% 18% 4	844
June	1st to 10th	Day	18% 10% 30% 28% 12% 3	780
	11th to 20th	Day	20% 11% 25% 28% 13% 2	780
	21st to end	Day	11% 7% 26% 32% 19% 5%	780
July	1st to 10th	Day	12% 5% 23% 36% 20% 4	771
	11th to 20th	Day	13% 5% 27% 32% 20% 3	768
	21st to end	Day	6% 6% 28% 36% 19% 6%	781
August	1st to 10th	Day	12% 6% 25% 31% 20% 5%	567
	11th to 20th	Day	11% 4 27% 34% 20% 5%	557
	21st to end	Day	10% 8% 22% 32% 21% 7%	627
September	1st to 10th	Day	14% 9% 28% 29% 14% 6%	570
	11th to 20th	Day	18% 7% 23% 29% 17% 6%	543
	21st to end	Day	13% 15% 32% 29% 9% 2	530
October	1st to 10th	Day	16% 8% 31% 27% 13% 4	445
	11th to 20th	Day	11% 14% 36% 26% 11% 3	330
	21st to end	Day	14% 16% 37% 23% 9% 2	363
November	1st to 10th	Day	15% 12% 34% 29% 8% 2	330
	11th to 20th	Day	15% 12% 40% 23% 7% 2	281
	21st to end	Day	9% 11% 37% 26% 12% 5%	220
December	1st to 10th	Day	7% 11% 41% 28% 10% 3	220
	11th to 20th	Day	10% 13% 43% 21% 11% 3	220
	21st to end	Day	6% 8% 36% 30% 17% 2	242
January	1st to 10th	Night	8% 11% 38% 30% 11% 1	1050
	11th to 20th	Night	8% 11% 43% 29% 8% 1	1045
	21st to end	Night	10% 14% 38% 29% 8% 1	924
February	1st to 10th	Night	9% 11% 33% 33% 11% 3	840
	11th to 20th	Night	9% 8% 37% 34% 11% 1	824
	21st to end	Night	7% 10% 34% 29% 17% 4	692
March	1st to 10th	Night	7% 8% 36% 34% 12% 3	840
	11th to 20th	Night	9% 8% 37% 33% 11% 2	840
	21st to end	Night	12% 7% 32% 35% 11% 2	924
April	1st to 10th	Night	13% 8% 31% 32% 15% 1	781
	11th to 20th	Night	15% 7% 35% 33% 9%	623
	21st to end	Night	17% 8% 30% 35% 10%	630
May	1st to 10th	Night	17% 11% 26% 31% 13% 1	519
	11th to 20th	Night	14% 7% 30% 35% 14% 1	414
	21st to end	Night	21% 5% 22% 33% 18%	455
June	1st to 10th	Night	20% 7% 30% 29% 14%	420
	11th to 20th	Night	20% 4 30% 34% 12% 1	420
	21st to end	Night	12% 4 21% 45% 18% 1	420
July	1st to 10th	Night	9% 4 17% 43% 26% 1	410
	11th to 20th	Night	12% 4 24% 40% 18% 2	408
	21st to end	Night	6% 4 20% 43% 24% 2	460
August	1st to 10th	Night	11% 3 14% 43% 27% 2	418
	11th to 20th	Night	10% 2 19% 44% 22% 2	584
	21st to end	Night	10% 4 22% 42% 22% 1	693
September	1st to 10th	Night	14% 4 23% 38% 20% 2	735
	11th to 20th	Night	15% 5% 20% 39% 19% 2	812
	21st to end	Night	13% 6% 32% 34% 14% 2	800
October	1st to 10th	Night	13% 7% 29% 33% 16% 2	800
	11th to 20th	Night	12% 6% 34% 33% 12% 2	800
	21st to end	Night	11% 10% 34% 35% 8% 1	880
November	1st to 10th	Night	14% 10% 38% 28% 9% 1	937
	11th to 20th	Night	9% 11% 45% 26% 7% 1	1050
	21st to end	Night	9% 11% 41% 31% 8% 2	1050
December	1st to 10th	Night	10% 11% 40% 27% 11% 2	1050
	11th to 20th	Night	6% 10% 41% 33% 7% 1	1050
	21st to end	Night	8% 10% 39% 32% 9% 2	1155

Page generated at 2026-09-11 02:11:52. Version ac07

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